The inhomogeneous distribution of Mn content can also be
found in different regions of the same sample. Fig. 6 shows the
normalized CL spectra performed at 100 K on structures located
in different positions of the pellet. The spectrum marked as number
1 corresponds to a region close to the Ar inlet. In this case, the
spectrum shows the typical features related to pure ZnO, although a
small increase of luminescence intensity can be distinguished in the
green region. In the CL spectrum recorded at increasing distances
of the inlet (spectra 2 and 3), the 2.37 and 1.8 eV bands are clearly
visible and their intensity increases with the distance. Finally, in
the regions of the pellet in the opposite side to the Ar inlet (spectrum
4) the band centered at 2.37 eV is the most intense which
could be related to a higher contribution of a spinel phase to luminescence
emission